The goal of this project is to develop, validate, and apply an organ culture bioreactor system to study the role of humoral (circulating) agents in valvular extracellular matrix (ECM) remodeling. The broad long-term objectives of our research are to understand the causes and progression of heart valve disease, to improve therapeutic options, and to reduce the incidence of valve disease. Although heart valve disease necessitated 96,000 surgeries in the U.S. last year, experimental research on its pathogenesis has been scant. There are also few studies about remodeling elicited by pharmacological, toxic, or naturally occurring chemicals in the circulation, despite evidence that such mechanisms exist, particularly with the serotonergic drugs fenfleuramine (weight loss) and pergolide (Parkinson's syndrome). Our hypothesis is that humoral agents induce valvular remodeling, and that valvular organ cultures grown in a bioreactor will provide novel spatial and temporal information about remodeling mechanisms. These hypotheses will be tested by implementing the following specific aims: (1) Design a simple mechanical conditioning bioreactor for organ culturing mitral valves, (2) Assess and optimize the bioreactor's ability to maintain the in vivo characteristics of normal valves based on an evaluation of the material properties, microstructure, ECM, and cell phenotypes in the organ cultured valves, and (3) Compare the remodeling of the organ cultured valve tissues after configuring the bioreactor to simulate serotonergic drug-induced valvulopathies. Demonstrating that humoral agents can induce remodeling in heart valves and then suggesting regulatory mechanisms would usher valve study into the field of integrative physiology, enable the development and testing of therapeutic agents, and could alleviate the need for surgical intervention. Additionally, the organ culture bioreactor system would permit unlimited future biologically and clinically focused studies of normal, diseased, surgically repaired, medically treated, and tissue engineered heart valves. Relevance: Certain popular serotonin-like medications enter the blood and cause heart valve disease, but their valve damaging activities are unclear. Our plan to grow pig heart valves in an incubator and expose them to these drugs will help us understand the drugs' actions. In the future, similar methods can be used to screen potentially damaging drugs and to understand other valve diseases - both essential to public health. [unreadable] [unreadable]